DNS considerations for service by remote systems

When you configure a secondary zone or stub zone for an HCP system, you specify a domain name and the IP addresses of the primary name servers for the applicable HCP domain. This causes client requests that identify the system by that domain name to be forwarded to those primary name servers.

Namespaces can be configured to accept client requests on HCP systems other than the system targeted by the request when that system is unavailable. To enable this redirection to occur automatically for a namespace:

• DNS failover must have been enabled on the target system.
• The applicable replication link must be failed over. The applicable replication link is the link between the target system and the system to which requests must be redirected.
  Attention: DNS failover affects all the tenants on an HCP cluster. For DNS failover to succeed, all Active-Active and Active-Passive links must fail over to the target system. If the HCP cluster has tenants that are not part of a replication link, or if the tenant is on a replication link that has not failed over, write requests to the tenant and read requests from the tenant fail if the domain name is used in the request. Requests will succeed if the request includes the IP address of the primary cluster instead of the domain name.
• The applicable secondary zone or stub zone for the target system must include the IP addresses of the applicable primary name servers for the system to which requests must be redirected, where:
  • The applicable secondary zone or stub zone on the target system is the one defined for the data network for the tenant that owns the namespace
  • The applicable primary name servers for the system to which requests should be redirected are the ones included in the secondary zone or stub zone for the network with the same name as the tenant data network on the target system

  For examples, you may suppose:

• The data network for a tenant is the network named net1.
• The system targeted by a client request has primary name servers with IPv4 addresses 192.168.210.15, 16, 17, and 18 and with IPv6 addresses 2001:0db8::101, 102, 103, and 104 for net1. The system to which requests must be redirected has primary name servers with IPv4 addresses 192.168.24.72, 73, 74, and 75 and with IPv6 addresses 2001:0db8::201, 202, 203, and 204 for net1.
• The system targeted by a client request has primary name servers with IPv4 addresses 192.168.210.15, 16, 17, and 18 and with IPv6 addresses 2001:0db8::101, 102, 103, and 104 for net1. The system to which requests must be redirected has primary name servers with IPv4 addresses 192.168.24.72, 73, 74, and 75 and with IPv6 addresses 2001:0db8::201, 202, 203, and 204 for net1.

In this case, the secondary zone or stub zone for net1 on the target system have these IP addresses:

192.168.210.15
          2001:0db8::101
          192.168.210.16
          2001:0db8::102
          192.168.210.17
          2001:0db8::103
          192.168.210.18   
          2001:0db8::104
          192.168.24.72
          2001:0db8::201
          192.168.24.73
          2001:0db8::202
          192.168.24.74
          2001:0db8::203
          192.168.24.75
          2001:0db8::204